One proposed structure of the power output apparatus includes an internal combustion engine, two motors, a Ravigneaux planetary gear mechanism, and a parallel shaft-type transmission arranged to selectively connect one of two output elements of the planetary gear mechanism, which are respectively connected to the two motors, to an output member (see, for example, Patent Document 1). Another proposed structure of the power output apparatus has a planetary gear mechanism including an input element connected with an internal combustion engine and two output elements respectively connected with two motors, and a parallel shaft-type transmission including two countershafts respectively connected with the corresponding output elements of the planetary gear mechanism and selectively connected with an output shaft (see, for example, Patent Document 2). In the power output apparatuses of these prior art structures, the parallel shaft-type transmission changes over the output element of the planetary gear mechanism to be connected to the output member or the output shaft. Such changeover of the connection varies a torque fraction transmitted to the output member or the output shaft out of the whole output torque of the internal combustion engine.    Patent Document 1: Japanese Patent Laid-Open No. 2005-155891    Patent Document 2: Japanese Patent Laid-Open No. 2003-106389